Microstructure characterisation of biphasic titanium alloy Ti–10V–2Fe–3Al and effects induced by heterogeneities on X-ray diffraction peak’s broadening

Abstract

The present study deals with a microstructural characterisation of a biphasic titanium alloy Ti–10V–2Fe–3Al. The near β titanium alloy is primarily used for high strength applications, such as components for aeronautical industry. The forging process and the heat treatments of Ti–10V–2Fe–3Al induce a complex microstructure, which consists of an equiaxial primary phase α_p (hcp) and a secondary phase α_sec (hcp) precipitating in the cubic phase β matrix. The forged material exhibits some structures hundreds of micrometres in size. Microstructure evolutions of forged and milled samples are analysed using a scanning electron microscope. Superficial treatments on forged and aged components induce a microstructure flow on the surface. Crystallites’ sizes and strain between phases are heterogeneous, and thermomechanical treatments may induce preferred crystallographic orientations. These phenomena broaden peaks strongly and generate difficulties in analysing residual stresses by X-ray diffraction. The present paper presents the microstructure’s evolution, linked to diffraction peaks broadening and crystallographic textures analyses.

Keywords:

• X-ray diffraction
• Titanium alloys
• Residual stresses
• Plastic deformation
• Textures
• End milling

Eurocopter Marignane supplied Ti–10V–2Fe–3Al material. X-ray diffraction analyses and micrograph were carried out at MecaSurf Laboratory, Arts et Metiers ParisTech (Aix-en-Provence, France). Analyses by MEB-SEM at the EADS IW (Suresnes, France) and MET analyses at IM2NP UMR 6242 CNRS Marseille Saint Jerome University were supported by Eurocopter Marignane. Sincere thanks are due to MecaSurf, Eurocopter Marignane, EADS IW and IM2NP staffs, without whose help the study would not have been possible.